The medieval mathematicians of Oxford, toiling in torchlight in a land ravaged by plague, managed to invent a simple form of calculus that could be used to track the motion of heavenly bodies. But now a scholar studying ancient clay tablets suggests that the Babylonians got there first, and by at least 1,400 years.

The astronomers of Babylonia, scratching tiny marks in soft clay, used surprisingly sophisticated geometry to calculate the orbit of what they called the White Star — the planet Jupiter. Most strikingly, the methodology for those computations used techniques that resembled the astronomical geometry developed in the 14th century at Oxford. The tablets have been authoritatively dated to a period from 350 B.C. to 50 B.C.

Plastic may be hurting oysters

Tiny bits of plastic in the ocean could have a serious impact on the ability of oysters to reproduce, a new study suggests, affecting everything from the movement of their sperm to the growth of their babies. The study is just the latest in a long string of research on the harmful effects of plastic on marine organisms.

The problem is that when plastic is dumped into the ocean, it doesn’t decompose — rather, it breaks down into pieces. Once it reaches fewer than 5 millimeters in diameter, it’s referred to as “microplastic.” Oysters then eat the microplastics. Oysters that were exposed to microplastics produced fewer and smaller egg cells and slower sperm, the researchers said in a study published in the Proceedings of the National Academy of Sciences. Exposed oysters also produced fewer larvae — about 41 percent fewer, in fact — and their offspring tended to grow more slowly.

An early taste for tortoises

More than 400,000 years ago, hunter-gatherers living in what is now Israel perked up a diet of game and vegetables with tortoises.

“The evidence shows they regularly ate turtle,” said Ran Barkai, an archaeologist at Tel Aviv University. “It was a sort of supplementary dish, maybe like a dessert or an opener to dinner.”

Inside the Qesem Cave near Tel Aviv, Barkai and his colleagues discovered the remains of turtle shells with burns, as well as tortoise bones with markings left by stone tools. The remains suggest that the inhabitants sometimes roasted tortoises whole over a fire and sometimes butchered them first, Barkai said, adding, “Somehow they cut them with stone knives.”

Qesem Cave was discovered during a road construction project in 2000 and has proved to be a trove of ancient tools and fossils.

The inhabitants were hunter-gatherers who came and went from the cave. They hunted mainly game animals like fallow deer, wild horses and cattle. Evidence suggests they also ate vegetable material. “What we know now is that they also had turtle on the menu,” Barkai said.

The findings appear in the journal Quaternary Science Reviews. He and his colleagues are now studying the remains of bird bones discovered in the cave.